Electro-sensitive planographic printing plate



May 9, 1961 H. R. DALTON ErAL 2,983,220

ELECTRO-SENSITIVE PLANOGRAPHIC PRINTING PLATE Filed March 1e. 1955 1N VEN TORS. HAROLD IQ. @ALTO/V MU/QQA V WOLF DI? EK United States PatentELECTRO-SENSITIVE PLANOGRAPHIC PRINTING PLATE Filed Mar. 16, 1955, Ser.No. 494,683

7 Claims. (Cl. lOl-149.2)

This invention relates to exible base electro-responsive planographicprinting plates and to the methods of manufacture and compositions ofsuch planographic plates.

A principal object of the'inyention is to provide an electro-responsiverecording blank which may have an image of subject matter producedthereon in response to the action of electric currents or potentialsapplied thereto, such for example as telefacsimile signals and the like,and which imaged blank may subsequently be used as a planographicprinting plate on a planographic printing press.

In the art ofl imaging cellulosic-base planographic printing plates ithas been common to type images with specially prepared typewriterribbons, or write on these plates with specially prepared pencils,crayons or inks. Such cellnlosic-base planographic printing plates,often referred to in the art as direct image planographic printingplates or masters, may also be imaged by preprinting them usingspecially prepared preprinting inks.

Accordingly, another object of this invention is to produce acellulosic-base planographic printing plate which can not only be usedin conjunction with stylusapplied electric signals but will be useful aswell for receiving an image as indicated above by typing or printing,etc.

Another object of this invention is to produce a cellulosic-baseplanographic printing plate having an electrically conductingbasecoating, an electrically conducting intermediate coating ofhydrophilic character, and a resinous top coating containing for examplea vinyl acetate maleic acid copolymer or vinyl methyl, vinyl ethyl orvinyl isobutyl ether maleic acid copolymer, said top coating beingrendered water resistant. l

Another object of this Vinvention is to produce a cellulosic-baseplanographicV printing plate having an electricallyy conductingintermediate coating of hydrophilic character and a resinous top coatingcontaining for example a vinyl methyl, vinyl ethyl, or vinyl isobutylether maleic acid copolymer in which one of the acid groups of themaleic acid has been converted to a methyl or ethyl ester, said topcoating being rendered water resistant.

Another object of this invention is to produce a cellulosic-baseplanographic printing plate having an electrically conducting basecoating, an electrically conducting intermediate coating of hydrophobiccharacter and a top coating containing a resinof the type abovedescribed, which coating has been rendered water resistant. Y

Another object of this invention is to produce a planographic printingplate in which the base support is a metal or electrically conductingpaper or film to which is applied a top coating containing a resin ofthe type above described, which coating has been rendered Waterresistant with an aluminum or ferric salt,

Y A feature of the invention relates to the novel combination of theseveral compositions of coatings applied 'to a ilexible backing-wherebythere is produced an rf' ICC electro-sensitive image-forming blank whichcan also be used as a planographic master.

Another feature relates to a planographic printing plate having anexposed surface coat which is hydrophilic and water resistantandconsisting mainly of a vinyl maleic acid copolymer resin, with orwithout a light colored pigment.

As shown in the drawing, the recording and printing plate comprises abase 1 consisting of paper or any other pliable material or llm. To thepliable material or film is applied three coatings or layers. Thecoating 2 directly over the base support is formulated Yso that it notonly has the correct electrical resistance to render the plateselectively responsive to stylus-applied potentials, but will also actas a water-impervious layer or water barrier which will keep thesupport, in the case of paper, from becoming wet and dimensionallyunstable when the nished plate is dampened during the planographicprinting process. The layer or coating 3, herein referred to as theintermediate coating, has the proper electrical resistance so thatstylus-applied currents will perforate elemental areas in the surface ofthe plate leaving a clear, sharp image thereon but without perforatingthe base 1. The intermediate coat may be either hydrophilic orhydrophobic in character. The top layer or coating 4, referred to hereinas the lithographie coating, has two purposes. The main purpose is thatof serving as a lithographie surface which will attract and hold waterin the non-imaged or un-recordedareas,Y as is Well-known in the art ofplanographic printing. The second is that of providing a coating whichcan be made light in color with a suitable pigment so that the darkimaged areas will be clearly visible. This contrast is not howeveressential to the operation of the plate. Furthermore, if desired, theintermediate coating 3 may be eliminated if a base 1 having electricalconducting properties is used. Y

As disclosed in U.S. Patent 2,664,044, the base paper or support may beof a'conducting or non-conducting type, whereby it is madeelectro-sensitive for the recording Vof electrical signals to make aduplicating blank by electro-optical scanning arrangements alsoasdisclosed in said Patent'2,664,044.v It is preferable that thesupport, if paper, be so treated by well-known methodsas to possess wetstrength. l

In accordance with this invention the electrically conducting coating 2comprises, for example, acetylene black or other electrically conductingcarbon black, mixed withY a suitable binder such as polyvinylchloride,pol`y vinyl acetate, acrylonitrile polymers, cellulose ethersor esters, copolymer of vinyl chloride, vinyl acetate, vinylidenechloride, polymers, etc. The binder for the intermediate layer orcoating 3, the solvent for this coating, and the method of applicationshould be such that there will be no tendency for the base coating 2 tobe deleteriously alected by the application of coating 3. Furthermore,the resin, solvent and method of Vapplication ofv the lithographiccoating 4l should be such that neither of the two previous coatings 2 or'3 be deleteriously affected by the application of coating 4.

Since the lithographie coating will be the one which is exposed duringsubsequent handling or'printing, it is important that the binder usedfor this coating be resistant to water or capable of being renderedwater resistant by subsequent treatment, otherwise Vthe printing platewould not only spot and smear vduring handling but the lithographiecoating would bedisturbed or washed away during the dampening cycle ofthe planographic printing process.

The following is a typical example, but not by way of limitation, of aformulation which can be used for the base coating 2. Another example isgiven in U.S. Pat- Y 3 ent No. 2,664,043, to Harold R. Dalton, assignedto the assignee of the persent application.

First example forvcoatng 2 30.0 grams of Vinylite VYNS (manufacturedbythe Bakelite.Corporatiolnvinyl chloride-vinyl acetate copolymer-.90percent chloride) (average molecular weight 15,000)

30.0 gramsV of acetylene black (Shawinigan Products Corporation) 400.0gramsof methyl ethyl ketone Y v The coating is easily prepared bydissolving the Vinylite resin in the methyl ethyl ketone. The solutionis poured into a yball mill jar to which is also added the acetyleneIblack. The mixture is milled for a period of 24 hours. The coating islapplied to the paper by any of the usual methods which includesspraying, dipping, knife coating, roller coating, etc. After the coatinghas been applied the'solvent is evaporated by heating or other suitablemethod leaving behind a dry smooth coating on the paper. f

The following is another example of the formulation that can be used forcoating 2.

Second example for coating 2 15.0 grams V-inylite VYDR (manufactured bythe Bakelite Corporation, vinyl'chloride-vinyl acetate copolymer-96percent vinyl chloride) (average molecular weight 24,000)

15.0 grams acrylonitrile-butadiene rubber (35 percent acrylonitrilemanufactured by Goodrich Tire and Rubber Co.) v

376.0 grams methyl ethyl ketone 75 .0 grams of methyl isobutyl ketone50.0 grams acetylenejblack (Shawinigan Products Corporation) 15.0 gramsdi-octyl phthalate Y 6.0 grams Acrawax (octadecanoicamide) =(GlycoProducts Co.)

The Vinylite resin is dissolved in a mixture of 290.0 grams of methylethyl ketone and 75.0 grams of methyl isobutyl ketone. The rubber isdissolved in 61 grams of methyl ethyl ketone while the Acrawax isdissolved in the remaining 25.0 grams of methyl ethyl ketone with aslight amount of heating. These solutions and the other ingredients Vareadded to a ball mill jar and the mixture milled for 24 hours. Thiscoating is applied to the paper lby any'ofthe 'methods previously named,again followed by drying.

As already stated, the intermediate coating 3 may be eitherhydrophilicor hydrophobic in character. A few examples of hydrophilic resins Vwhichcan be used for the intermediate coating 3are casein, soya protein,gelatine, hydroxyethylcellulose, polyvinyl acetate, polyvinyl alcohol,etc.' A few examples of hydrophobic resins which can be used for `theintermediate coating 3 are methacrylates, methyl methacrylates, styrene,polyvinyl chloride-acetate, polyvinyl chloride, polyvinylidene chloride,urea formaldehyde,gcellulose esters and ethers, etc.

The following is a typical example of a formulation which can be usedfor the intermedaite coating 3 having hydrophilic properties.

First example for coating 3 (hydrophilic) 20.0 grams`Gelva C3 resin(grade V-30 modified polyvinyl acetate manufactured by ShawiniganProducts Corporation) Y 20.0 grams Elvanol`20-105 resin (polyvinylalcohol,

inigan Products Corporation) 'I'he Elvanol was dissolved in 180.0 gramsof hot methanol. The Gelva is dissolved in the remaining 100.0 gramsofmethanol. The two solutions and the carbons are added to a ball mill jarand milled for 24 hours. This formulation is applied over base coating 2as already described Y'byany of the methods cited under the examples forcoating 2. After the coating operation, it is necessary to evaporateagain the excess solvent by heat or any other suitable method.V

The following is a formulation which can be used for the intermediatecoating 3 having hydrophobic properties.

Second example for coating 3 (hydrophobic) 20.0 grams of butylmethacrylate polymer (Hypolon P-4, E. I. du Pont de Nemours Co.)

100.0 grams of Toluso (Shell Chemical Co.) 2.66 grams of gas black(Dixie No. 5, United Carbon 0.33 grams of acetylene black (ShawiniganCorp.)

The butyl methacrylate is dissolved in the Tolusol (mixture of straightchain and cyclic hydrocarbons) and added to the carbon in a ball milljar. The mixture is milled for 24 hours. The coating is applied over thebase coating 2 by means previously described and heated to drive olf thesolvent and leave a dry coating.

Another example of a formulation which may be used for the intermediatelayer 3 is as follows: this formulation will produce a coating havinghydrophilic properties.

Third example for coating 3 (hydrophilic) 80.0 grams Protovac PV8979(modified casein manufactured by theV Borden Co.)

560.0 grams of water 20.0 grams of formaldehyde (8 percent solution) 0.8grams of Dowicide-G (sodium pentachlorophenolate, manufactured by DowChemical Co.)

12.0 cc. of ammonia (28 percent) 2.0 grams of Nopco 1497-V a waterdispersion of fats and fatty acids (National Oil Products Co.)

1.33 grams of acetylene black (Shawinigan Products Corp.)

106.7 grams of gas black (Dixie No. 5, United Carbon The Protovac PV8979is dispersed in hot water for 30 minutes under mild agitation. At thispoint the ammonia is added to dissolve the Protovac PV8979. When thissolution has cooled, it is added to the other ingredients which are in aball mill jar. The mixture is milled for 24 hours. This mixture iscoated over the base coating 2 by any of the aforesaid methods andheated to drive olf the solvent which is water in this instance.

The resins already mentioned for use in the lithographie coating 4 canbe formulated to produce a permanent bond with the intermediate coatingsmentioned. In addition the lithographie coating in its final form isresistant to water and possesses a hydrophilic tendency over its entiresurface as will be discusssed below. Such resins as casein, sodiumalginate, gelatine, carboxylmethyl cellulose polyvinyl alcohol, etc.,have been used in the past for preparing the top coatings for directlimage planographic printing plates. Any one of these resins may be usedin the lithographie coatings of the electro-responsive planographicprinting plate described. However, the poor recordingelectro-sensitivity properties of these materials makes them undesirablefor commercial use.

Products It has been foundthat if the resin binder used in the..y

lithographie coating is a copolymerization product of (A) vinyl acetateand maleic acid, or (B) vinyl methyl, vinyl ethyl, or vinyl isobutyl.etherV and maleic acid, or (C) vinyl methyl, vinyl ethyl, Yor vinylisobutyl ether and ythe half methyl or ethyl ester of maleic acid, theelectrosensitivity and imaging ability of the electro-responsiveplanographic printing plate is greatly'improved. In addition, thesematerials, when used in a lithographie coating, retain all of thedesirable properties required of such a coating, namely a hydrophiliccharacter over its entire surface, water resistance upon being treatedafter deposition, the ability to repel ink once the coating is wet, andreceptivity to other imaging mediasuch as lithographie crayon when thecoating is dry.

'I'lhese copolymers are easily used in the preparation of thelithographie coating since they are readily soluble in hot water or verydilute alkali. The dried coating continues to remain water soluble sothat a subsequent operation is required to give the coating waterresistance. It has been found that it is necessary to treat the driedlithographie coating with an insolubilizing material for example asolution of a heavy metal salt such as an aluminum salt or ferrie ironsalt. These may be used in concentrations of 5 percent to 25 percent inwater and applied over the top lithographie coating in amounts to givethe coating the necessary water resistance.

A typical formula which may be used as a lithographie coating accordingto the present invention and also on direct image planographic platesmay be prepared from the following materials.

F rst example for coating 4 16.0 grams of polyvinyl methyl ether-maleieanhydride copolymer (manufactured by General Aniline and FilmCorporation) 48.0 grams of zinc oxide 48.0 grams of zinc sulfide 432.0grams of Water The coating is prepared by 4dissolving the copolymer ofpolyvinyl methyl ether and maleie anhydride in boiling water. Thesolution is cooled and added to the zine pigment which has been placedin a ball mill jar. The materials are milled for 24 hours. This coatingis applied over the intermediate layer 3 by any means described underthe above examples and heated to drive off all the water. The driedcoating is then treated with a percent water solution of a ferrie saltsuch for example as ferrie chloride hexahydrate by dipping, spraying,brush coating, roller coating, wire coating, air knife coating, etc.,followed by the application of heat to drive olf the water remaining inthe coatings and on the surface of the plate.

Another combination of materials that can serve as a lithographiecoating on electro-responsive planographic printing plates is preparedas follows.

Second example for coating 4 16.0 grams of polyvinyl acetate-maleicanhydride copolymer 48.0 grams of zinc oxide 48.0 grams of zinc sulfide336.0 grams of water 0.9 grams of sodium hydroxide The polyvinylacetate-maleic anhydride copolymer is dissolved in Water to which thesodium hydroxide had previously been added. The solution is then placed,along with the zinc pigments, into a ball mill jar and milled for 24hour-s. The coating is applied over the intermediate coating 3 by any ofthe aforementioned methods and heated to evaporate the water. When thecoating is dried, it is made resistance to Water by treatment withvvinyl methyl ether-maleie anhydride to react in methanol for 24 hours atroom temperature or by refluxing it with methanol until the reaction iscomplete.

T hiral example for coating 4 8.0 grams of polyvinyl methyl ether-maleicanhydride half methyl ester copolymer 168.0 grams of methanol 24.0 gramsof zinc oxide 24.0 grams of zinc sultlde The ingredients are placed in aball mill and milled for 24 hours. The coating is then applied over theintermediate layer 3 by any method described in previous examples audheated to drive otf the solvent. Since the coating made using the halfesters is still non-resistant to water at this point, it must be treatedwith a water solution of Iferrie or aluminum chloride in water' andagain heated to evaporate all traces of solvent. The above mixture mayalso be used as a lithographie coating for direct image planographicprinting plates, that is plates which are not required to beelectro-sensitive.

What is claimed is:

l. A planographic printing plate comprising, a backing having an exposedWater insoluble, hydrophilic lithographic surface coat consisting mainlyof a copolymer of maleic acid and one or more vinyl ethers chosen fromthe group consisting of vinyl methyl ether, vinyl ethyl ether, vinylisobutyl ether, and the half methyland half ethyl esters of the saidethers, and an electrically conductive water barrier coat containingpowdered conductive carbon with a resin binder and located between 4said backing and said lithographie surface.

2. A planographic printing plate according to claim l in which thebacking comprises Wet strength paper.

3. A planographic printing plate according to claim 1 in which thebacking is of wet strength paper, andin which another conductive resincoating is located between said water barrier coat and said lithographiecoat.

4. A blank which is electro-sensitive to stylus-applied electricpotentials to form a planographic printing master, comprising a backingof cellulosic material, an electrically conductive base coat on saidbacking, an electrically conductive intermediate coat, and a resinoushydrophilic, lithographie top surface coat containing a copolymer ofvinyl ether and maleic acid and wherein the vinyl ether has been chosenfrom the group consisting of vinyl methyl ether, vinyl ethyl ether,vinyl isobutyl ether, and the half methyl and half ethyl esters of thesaid ethers, said top surface coat being water resistant by havingincluded therein an insolubilizing salt of a heavy metal.

5. A blank according to claim 4 in which said salt is a ferrie salt.

6. A blank according to claim 4 in which said salt is an aluminum salt.Y

7. A blank which is electro-sensitive to stylus-applied electricpotentials to form a planographic printing master, comprising acellulosic backing, an electrically conductive base coat on saidbacking, an electrically conductive intermediate resinous coat, and aresinous lithographic top surface coat which is water resistant andcomprising a copolymer of a vinyl ether and maleic acid in which one ofthe maleie acid groups has been converted to an ester and lthe vinylether has been chosen from the group consisting of vinyl methyl ether,vinyl ethyl ether, vinyl isobutyl ether, and the halfv methyl and halfethyl esters of the said ethers, said top lithographic surface coatincluding an insolubilizing salt of a heavy metal'to render it Waterresistant.

References Cited in the file of this patent UNITED STATES PATENTSV2,186,946 Wood Jan. 16, 1940 2,251,742 Kline Aug. 5, 1941 (Otherreferences on following page) 7 UNITED 'STATES PATENTS' 2,713,822AlbersV et a1;` Aug. 4, 1942 2,721,815 Pene et a1. Aug. 29, 1944v2,756,163 Toland et Ya1. Dec. 5, 1950 5 Dalton Dec.' 29, 1953 Newman etal. Y Dec. 14, 1954 550,575

8 Newman 2- July 26, 1955 YYMullen Oct. 25, 11955 Herrick et a1. Jllly24, 1956 FOREIGN PATENTS Germani May 12, 1932

1. A PLANOGRAPHIC PRINTING PLATE COMPRISING, A BACKING HAVING AN EXPOSEDWATER INSOLUBLE, HYDROPHILIC LITHOGRAPHIC SURFACE COAT CONSISTING MAINLYOF A COPOLYMER OF MALEIC ACID AND ONE OR MORE VINYL ETHERS CHOSEN FROMTHE GROUP CONSISTING OF VINYL METHYL ETHER, VINYL ETHYL ETHER, VINYL,ISOBUTYL ETHER, AND THE HALF METHYL AND HALF ETHYL ESTERS OF THE SAIDETHERS, AND AN ELECTRICALLY CONDUCTIVE WATER BARRIER COAT CONTAININGPOWDERED CONDUCTIVE CARBON WITH A RESIN BINDER AND LOCATED BETWEEN SAIDBACKING AND SAID LITHOGRAPHIC SURFACE.
 3. A PLANOGRAPHIC PRINTING PLATEACCORDING TO CLAIM 1 IN WHICH THE BACKING IS OF WET STRENGTH PAPER, ANDIN WHICH ANOTHER CONDUCTIVE RESIN COATING IS LOCATED BETWEEN SAID WATERBARRIER COAT AND SAID LITHOGRAPHIC COAT.